Highly photosensitive titanium dioxide and process for forming the same

Abstract

A highly photosensitivity titanium oxide composition includes a plurality of nanosize particles including titanium dioxide and titanium suboxide. The particles are substantially non-stoichiometric (TiO 2-x , wherein 0.1<x<0.3 at a surface of the particles, and in the bulk of the particles x is less than at the surface), provide a magnetic susceptibility value (X) of at least 0.8 10 −6 cm 3 /g at 300 K, and are least 30% by weight rutile. A related method of forming a high photosensitivity titanium oxide composition includes the steps of providing a titanium chloride compound, such as titanium tetrachloride, an oxygen-containing gas and hydrogen, wherein a concentration of the hydrogen is in a stoichiometric excess (H 2 :O 2 ) from 2.02:1 to 2.61:1. The titanium chloride compound is burned in the presence of oxygen from the oxygen-containing gas and hydrogen to form plurality of ultrafine particles comprising titanium dioxide and titanium suboxide. The method can include the steps prior to the burning step of mixing the titanium chloride compound, oxygen and hydrogen and heating the same to 50 to 100° C., such as from 70-100° C.

1. A high photosensitivity titanium oxide composition, comprising:
 a plurality of nanosize particles comprising titanium dioxide and titanium suboxide, 
 said particles being substantially non-stoichiometric having a magnetic susceptibility value (X) of at least 0.8 ×10 −6  cm 3 /g at 300 K and being at least 30% by weight rutile. 
 
     
     
       2. The composition of  claim 1 , wherein said X is between 0.8 ×10 −6  cm 3 /g and 2.4 ×10 −6  cm 31 g at 300 K. 
     
     
       3. The composition of  claim 1 , wherein an average size of said particles is 10-40 nm. 
     
     
       4. The composition of  claim 1 , wherein said rutile is at least 40%, and a balance of said composition comprises anatase. 
     
     
       5. The composition of  claim 4 , wherein said composition comprises 45 to 55% of said rutile, said anatase comprising the balance. 
     
     
       6. The composition of  claim 1 , which further comprises chlorine, wherein the chlorine concentration at a surface of said particles is less than a chlorine concentration in a bulk portion of said particles. 
     
     
       7. The composition of  claim 6 , wherein said chlorine concentration at said surface of said particles is at least an order of magnitude less than said chlorine concentration in said bulk of said particles. 
     
     
       8. The composition of  claim 1 , wherein said composition comprises Ti0 2-x , wherein 0.15 <x<0.3 at a surface of said particles, and less than x in a bulk of said particles. 
     
     
       9. The composition of  claim 8 , wherein said x in said bulk of said particles is <0.1. 
     
     
       10. The composition of  claim 8 , wherein said x in said bulk of said particles is from 0.08 to 0.1. 
     
     
       11. The composition of  claim 1 , wherein a photocatalytic activity of said particles is 1.4-3.0 mg/ml·min·m 2  as measured in the reaction of methylene blue reduction. 
     
     
       12. A high photosensitivity titanium oxide composition comprising a plurality of nanosize particles comprising titanium dioxide and titanium suboxide, said particles being substantially non-stoichiometric having a magnetic susceptibility value (X) of at least 0.8 ×10 −6  cm 3 /gm at 300 K and being at least 30% by weight rutile, formed from a process comprising the steps of:
 providing a titanium chloride comprising compound, an oxygen-containing gas and hydrogen, wherein a concentration of said hydrogen is in a stoichiometric excess (H 2 :O 2 ) from 2.02: 1 to 2.61: 1, and 
 burning said titanium chloride comprising compound at a steady state temperature from 700 to 1100 ° C. in the presence of oxygen from said oxygen-containing gas and said hydrogen to form plurality of ultrafine particles comprising titanium dioxide and titanium suboxide. 
 
     
     
       13. The composition of  claim 12 , further comprising the step of steaming said particles at 150-220 ° C. to promote desorption of chlorine from the surface of said particles. 
     
     
       14. The composition of  claim 12 , wherein a molar ratio of said titanium chloride comprising compound to said H 2 is in a range from 1:4 to 1 :2. 
     
     
       15. The composition of  claim 12 , further comprising the steps, prior to said burning step, of mixing said titanium chloride comprising compound, said oxygen and hydrogen; and heating said titanium chloride comprising compound, said oxygen and hydrogen to 70-100° C. 
     
     
       16. The composition of  claim 1 , wherein said composition includes <0.1 wt % silica.